Smartcards, RFID devices, wearables and methods
Coupling frames comprising a conductive (metal) surface with a slit (S) or non-conductive stripe (NCS) extending from an outer edge to an inner position thereof, and overlapping a transponder device. A coupling frame with slit for coupling with an inductive or capacitive device (inductor or capacitor) may be used at any ISM frequency band to concentrate surface current around the slit. The coupling frame can be tuned to operate at a frequency of interested by introducing a resistive, inductive or capacitive element. The resonance frequency of the coupling frame can be matched to that of the transponder chip module to achieve optimum performance. Coupling frames with or without a transponder device may be integrated, overlapping, stacked or placed adjacent to one another to enhance system performance. Multiple coupling frames may be electrically isolated from one another by the application of a dielectric coating such Diamond Like Carbon (DLC).
1. An RFID device comprising:
an RFID chip (IC);
a module antenna (MA) connected to the RFID chip (IC);
a coupling frame (CF) having a slit (S) or non-conductive stripe (NCS) overlapping at least a portion of the module antenna (MA); and
a capacitor connected across the slit (S) or non-conductive stripe (NCS).
2. The RFID device of claim 1 , wherein:
the capacitor is disposed on the coupling frame.
3. The RFID device of claim 1 , wherein:
the slit (S) or non-conductive stripe (NCS) has an outer end and an inner end; and
the capacitor is connected at a selected position between the outer and inner ends of the slit (S) or non-conductive stripe (NCS).
4. The RFID device of claim 1 , wherein:
the RFID chip (IC) and module antenna (MA) are disposed in a transponder chip module (TCM) having a mold mass (MM); and
the coupling CF has an opening for the mold mass (MM) of the transponder chip module (TCM).
5. The RFID device of claim 1 , wherein:
the coupling frame (CF) comprises a conductive surface having the slit (S) or non-conductive stripe (NCS) extending through the surface from an outer edge thereof to an inner position thereof.
6. The RFID device of claim 5 , wherein the coupling frame (CF) is disposed in a card body (CB) of a smart card (SC).
7. The RFID device of claim 1 , wherein the slit (S) or non-conductive stripe (NCS) extends to an opening (OP) in the coupling frame (CF).
8. The RFID device of claim 1 , wherein the slit (S) or non-conductive stripe (NCS) overlaps at least some turns of the module antenna (MA).
9. The RFID device claim 1 , wherein:
the module antenna (MA) comprises an etched planar antenna (PA) having a number of tracks (traces) separated by spaces.
10. The RFID device of claim 9 , wherein:
a track width is less than 100 μm; and
a spacing between adjacent tracks is less than 75 μm.
11. A method of improving coupling between an RFID device comprising a transponder chip module (TCM) and an external reader, the transponder chip module (TCM) comprising an RFID chip (IC, CM) and a module antenna (MA), characterized by:
incorporating an open-loop conductive coupling frame (CF) in the transponder chip module (TCM), wherein the coupling frame (CF) has a slit (S) or non-conductive stripe (NCS) extending from an outer edge (OE) thereof to an interior position thereof and coupling frame (CF) is positioned so that the slit (S) or non-conductive stripe (NCS) overlaps at least a portion of the module antenna (MA, PA, LES); and
connecting a capacitor across the slit (S) or non-conductive stripe (NCS).
12. The method of claim 11 , wherein the coupling frame can be tuned to operate at a frequency of interested by introducing a resistive, inductive or capacitive element.
13. The method of claim 11 , wherein a resonance frequency of the coupling frame can be matched to that of a transponder chip module to achieve optimum performance.
14. The method of claim 11 , wherein coupling frames with or without a transponder device may be integrated, overlapping, stacked or placed adjacent to one another to enhance system performance.
15. The method of claim 11 , wherein multiple coupling frames may be electrically isolated from one another by the application of a dielectric coating such Diamond Like Carbon (DLC).
16. The method of claim 11 , wherein the capacitor connected across the slit accomplishes at least one of the following:
improve voltage delivery to the RFID chip; and
regulate at least one of the frequency response, bandwidth and Q factor of the complete system.